The present invention relates to well servicing fluids and, more particulary, to well servicing fluids of a water-in-oil emulsion type.
Water-in-oil (invert) emulsion well servicing fluids are becoming increasingly popular for drilling into producing formations, for workover operations, and for drilling through salt formations, as well as other instances where it is desirable to avoid exposing the formation to water as a continous phase of the well servicing fluid.
One of the most important properties of a well servicing fluid is that it must possess a low fluid loss, particularly a low water loss. Low water loss drilling fluids permit drilling into heaving shale or similar formations without causing such shale to swell and cave into the bore hole. Low water loss drilling fluids also prevent decreases in permeability due to water blocking of pore space. Low fluid loss water-in-oil emulsion type drilling fluids are particularly advantageous since the oil, being the continuous phase, protects the formation from the water contained in the drilling fluid.